Al-Kāfi

Hadith 682
wudu
4ـ أَبُو عَلِيٍّ الأشْعَرِيُّ عَنْ مُحَمَّدِ بْنِ عَبْدِ الْجَبَّارِ عَنْ صَفْوَانَ عَنِ الْعَلاَءِ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَحَدِهِمَا (عَلَيْهِما الْسَّلام) قَالَ سَأَلْتُهُ عَنِ الرَّجُلِ تَفْجَأُهُ الْجِنَازَةُ وَهُوَ عَلَى غَيْرِ طُهْرٍ قَالَ فَلْيُكَبِّرْ مَعَهُمْ.
4. Abu Ali al-Ash’ariy has narrated from Muhammad ibn ‘Abd al-Jabbar from Safwan from al-‘Ala’ from Muhammad ibn Muslim who has said the following: “I once asked one of the two Imam, (abu Ja’far or abu ‘Abd Allah), ‘Alayhim al-Salam, about a man who suddenly comes across Salah (prayer) for a deceased without Wudu’. He (the Imam) said, ‘He can say Takbir (Allah is great beyond description) along with them.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī